MCS with Eye - July 21, 2003

David RothForecasterWeather Prediction Center

This page was created to evaluate the precursor conditions to this unusual
MCS over land, and to describe
its effects across the eastern Great Lakes, Upper Ohio valley, and
northern Mid-Atlantic regions of the
United States.

1. Precursor conditions

All surface and upper level analyses shown below were performed
by members of the staff of the
Weather Prediction Center (WPC) in Camp Springs, MD.

An area of convection developed across eastern Iowa near a weak stationary/warm
front at 0302 GMT (image above),
and moved to the east along this old frontal boundary. By 1203
GMT (below), the convective system had matured,
taking on the shape of a wavy squall line across western Ohio and southern
Indiana.

At 250 hPa (below), the suspect area was in the right entrance
region of one upper jet streak, with a
stronger jet streak on its heels across the northern Plains, a very
favorable coupled jet structure. This led
to a significantly diffluent/divergent environment aloft, which allowed
the MCS to continue to evolve.

At 500 hPa (below), the trough is seen moving through the Ohio Valley,
with its axis was still across Indiana.

At 850 hPa and in the precipitable water fields (below), you can see
the moisture pooling across Ohio
Valley, Pennsylvania, and New York, continuing the development of the
MCS.

The surface analysis (below) shows the MCS as depicted with a trough
with a meso-high
quickly on its heels across southwest Ohio and southeast Indiana.

Due to the moisture present and daytime heating, thunderstorm activity
grew in coverage and
intensity across Kentucky at the tail of the outflow boundary, starving
the MCS of moisture and
causing it to weaken. Below is an image from 1503 GMT.

2. Formation of the eye feature

As the system moved away from the thunderstorm area over the Ohio Valley,
the system reintensified,
starting to form a large hook, with occasional hook echoes appearing
along its eastern side. This is also
the time when the cyclone became defined in the surface pressure and
wind patterns. Below is a radar
image from 1837 GMT, and the surface analysis from 1800 GMT.

The system became more impressive later in the day. By 1900 GMT,
the central pressure of the cyclone
had fallen to 1001 hPa. Below is an image from 2036 GMT,
and the surface analysis from 2100 GMT.

3. Death of the eye feature

By 2244 GMT, a squall line took shape along its band to the south.
This began to starve the inner
convection, which can be seen in the corresponding radar image from
that time.

By 0126 GMT, daytime heating had ceased, the squall line had run out
ahead of the low, causing
the entire convective structure to weaken (below).

4. Effects of the MCS

Rainfall was our main concern at the Weather Prediction
Center. Below is
an isohyetal map of the rainfall observed at cooperative weather sites,
in inches.

Below is a list of post storm reports, reported by their respective
WFOs from Ohio to New York.
They speak for themselves.

0145 PM YOUNGSTOWN
OH TORNADO
07/21/03 MAHONING
AN F1 TORNADO SKIPPED
ALONG AN 8 MILE PATH
THROUGH THE NORTHEAST
SECTION OF TOWN AVERAGING
50 TO 100 YARDS WIDE WITH
PEAK WINDS ESTIMATED
BETWEEN 75 AND 110 MPH.
NUMEROUS TREES WERE DOWNED,
SOME ON HOMES AND
BUSINESSES. A 2 STORY
CINDERBLOCK BUILDING WAS
BLOWN OVER AND A COUPLE OF
RAILROAD CARS WERE BLOWN
OFF THE TRACKS.

...F1 TORNADO CONFIRMED IN LYCOMING COUNTY ON MONDAY JULY 21...
A TEAM FROM THE NATIONAL WEATHER SERVICE OFFICE IN STATE COLLEGE
SURVEYED DAMAGE AND INTERVIEWED RESIDENTS AND EMERGENCY MANAGEMENT
OFFICIALS IN LYCOMING COUNTY TODAY. THE TEAM DETERMINED THAT AN F1
TORNADO DID TOUCH DOWN IN LYCOMING COUNTY ABOUT 530 PM MONDAY
AFTERNOON.

THE TORNADO FIRST TOUCHED DOWN ON FUNSTON ROAD IN LAIRDSVILLE WHERE
IT DID MOST OF ITS DAMAGE...TEARING A ROOF OFF A BARN AND CAUSING
MINOR DAMAGE TO A FEW HOMES. THE TORNADO THEN CROSSED ROUTE 118 AND
LITTLE MUNCY CREEK AND CONTINUED ALONG BEAVER RUN ROAD. THE DAMAGE
PATH ENDED ON SAVAGE HILL ROAD AS THE TORNADO LIFTED OFF THE GROUND.

THE TORNADO PATH WAS 5 MILES LONG. THE TORNADO REACHED ONE HALF MILE
WIDE AT ITS WIDEST POINT. BASED ON THE DAMAGE...THE TORNADO WAS AN
F1 WITH WINDS UP TO 90 MPH.

THE FUJITA SCALE RATES TORNADOES ON WIND SPEED AND DAMAGE. THE SCALE
FOLLOWS:

THE NATIONAL WEATHER SERVICE TEAM ALSO INVESTIGATED OTHER DAMAGE IN
NEARBY MUNCY AND ACROSS THE RIVER IN LEWISBURG IN UNION COUNTY. THE
DAMAGE IN BOTH LOCATIONS WAS DUE TO A COUPLE OF DOWNBURSTS. THE
DAMAGE IN MUNCY WAS LIGHT AND SPORADIC AND CONFINED TO FALLEN TREES.

IN LEWISBURG...THE DAMAGE WAS FAR MORE EXTENSIVE. HUNDREDS OF TREES
FELL IN LEWISBURG AND MANY OF THEM FELL ON HOMES. THERE WERE EVEN A
FEW HOMES THAT SUSTAINED WIND DAMAGE TO THEIR ROOF THAT WAS NOT DUE
TO TREES FALLING ON THEM. THE AMERICAN RED CROSS AND ANOTHER
BUSINESS LOST PART OF THEIR ROOF AS WELL.

REMEMBER...THE BEST WAY TO STAY ON TOP OF WEATHER DEVELOPMENTS IN
YOUR AREA IS TO STAY TUNED TO YOUR LOCAL NOAA WEATHER RADIO.

MANY COUNTIES ACROSS NORTHWEST PENNSYLVANIA EXPERIENCED EXTREMELY
STRONG WINDS DURING THUNDERSTORMS ON MONDAY AFTERNOON...21
JULY...2003. AN UNUSUAL STORM FOR JULY GENERATED THUNDERSTORMS WHICH
PRODUCED AN F0 TORNADO IN MERCER COUNTY AS WELL AS SEVERAL
MICROBURSTS. MEANWHILE...NEAR OIL CITY IN VENANGO COUNTY...A LARGE
AREA OF TREES WERE EITHER SNAPPED OR TOPPLED DUE TO A MACROBURST.

IN MERCER COUNTY...PENNSYLVANIA

AN F0 TORNADO TOUCHED DOWN AROUND 225 PM TO THE NORTHEAST OF
LAKE WILHELM AND TRAVELED NORTHEAST ACROSS THE NEW LEBANON AREA.
MANY TREES WERE SNAPPED OR TOPPLED. A MOBILE HOME PARK WAS HARD HIT
WITH TREE DAMAGE AND SOME MINOR STRUCTURAL DAMAGE. ONE EYE WITNESS
DRIVING ALONG ROUTE 173 SAW THE TORNADO AND DEBRIS JUST BEFORE IT
HIT THE AREA. THE PATH LENGTH WAS ESTIMATED TO BE ABOUT 3 MILES. THE
MAXIMUM WIDTH AROUND 80 YARDS. THE MAXIMUM ESTIMATED WINDS WERE
AROUND 70 MPH.

MEANWHILE...FARTHER TO THE NORTHEAST IN MERCER COUNTY IN THE TOWN OF
CARLTON...A MICROBURST OCCURRED. THE DAMAGE SWATH WAS APPROXIMATELY
ONE QUARTER SQUARE MILE. MANY VERY LARGE TREES WERE SNAPPED OR
TOPPLED IN THE SAME DIRECTION. SOME DAMAGE OCCURRED FROM TREES
FALLING ONTO HOUSES AND SHEDS. MAXIMUM ESTIMATED WINDS IN THIS
MICROBURST WERE ABOUT 75 MPH.

IN VENANGO COUNTY...PENNSYLVANIA

THIS SAME INTENSE THUNDERSTORM SYSTEM PRODUCED A LARGE MACROBURST IN
VENANGO COUNTY...PENNSYLVANIA. A LARGE AREA ABOUT 6 MILES IN LENGTH
BY ABOUT 2 TO 3 MILES WIDE HAD HUNDREDS OF TREES SNAPPED AND
TOPPLED. MANY TREES FELL ONTO HOMES...SHEDS AND SOME CARS. THE ROOFS
FROM SEVERAL FACTORIES WERE RIPPED OFF AND DEBRIS SCATTERED OVER A
LARGE AREA. SEVERAL SIGNS AND NUMEROUS POWER POLES WERE DOWNED.
MAXIMUM ESTIMATED WINDS WERE ABOUT 70 MPH. THE OIL CITY DOWNBURST
WAS THE LARGEST TO OCCUR IN THE NWS PITTSBURGH COUNTY WARNING AREA
SO FAR THIS YEAR.

IN ADDITION TO THE DAMAGE DESCRIBED ABOVE...THERE WERE SEVERAL AREAS
IN MERCER COUNTY FROM FARRELL ACROSS TO JEFFERSON TOWNSHIP AND IN THE
SUGAR CREEK AREA OF VENANGO COUNTY THAT EXPERIENCED DOWNBURST WIND
DAMAGE. TREE DAMAGE ALSO OCCURRED ACROSS PARTS OF FOREST...JEFFERSON
...ARMSTRONG...BEAVER...LAWRENCE...BUTLER...AND ALLEGHENY
COUNTIES...AS WELL AS BELMONT...COLUMBIANA...AND JEFFERSON
COUNTIES...OHIO. HOWEVER...THE HIGHEST CONCENTRATION OF DAMAGE
OCCURRED IN MERCER AND VENANGO COUNTIES...PENNSYLVANIA

A DOWNBURST IS A STRONG WIND GUST ON OR NEAR THE GROUND WHICH IS
GENERATED BY A THUNDERSTORM. A MACROBURST IS A DOWNBURST THAT
PRODUCES A SWATH OF DAMAGE 2.5 MILES OR GREATER IN WIDTH. A
MICROBURST IS A DOWNBURST WHICH PRODUCES A SWATH OF DAMAGE LESS THAN
2.5 MILES WIDE. DOWNBURSTS OCCUR MUCH MORE FREQUENTLY THAN TORNADOES
AND THEY CAN PRODUCES MORE DAMAGE OVER A LARGER AREA THAN SMALL
TORNADOES.

LAST YEAR IN THE COUNTY WARNING AREA OF THE NATIONAL WEATHER SERVICE
IN PITTSBURGH...THERE WERE 9 CONFIRMED TORNADOES. THEY WERE
RESPONSIBLE FOR 1 FATALITY AND 23 INJURIES. MEANWHILE...OVER 16
SIGNIFICANT DOWNBURSTS OCCURRED WHICH CAUSED 2 FATALITIES AND ALMOST
70 INJURIES.

SO FAR THIS YEAR...TWO CONFIRMED TORNADOES HAVE OCCURRED ACROSS THE
NWS PITTSBURGH COUNTY WARNING AREA. THE SCOTT TOWNSHIP AND GREENTREE
F0 ON 12 JUNE AND THE NEW LEBANON F0 YESTERDAY.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
545 PM EDT TUE JUL 22 2003

...F3 TORNADO CONFIRMED IN POTTER COUNTY ON MONDAY JULY 21...

A TEAM FROM THE NATIONAL WEATHER SERVICE OFFICE IN STATE COLLEGE
SURVEYED DAMAGE AND INTERVIEWED RESIDENTS AND EMERGENCY MANAGEMENT
OFFICIALS IN POTTER COUNTY TODAY. THE TEAM DETERMINED THAT AN F3
TORNADO DID TOUCH DOWN IN POTTER COUNTY AROUND 400 MONDAY AFTERNOON.

THE TORNADO FIRST TOUCHED DOWN ABOUT 2 MILES SOUTHWEST OF THE TOWN
OF ELLISBURG...WHERE IT DOWNED HUNDREDS OF TREES. THE TORNADO
CONTINUED TO THE NORTHEAST...WHERE IT HIT THE SMOKER FARM. THE BARN
AND HOUSE WERE COMPLETELY DESTROYED...AND ONE OF THREE SILOS WAS
TIPPED OVER. A SECOND HOME ON SMOKER ROAD WAS ALSO EXTENSIVELY
DAMAGED AND IS UNINHABITABLE. IN ADDITION...A CAR WAS PICKED UP AND
THROWN 600 YARDS. A FARM TRACTOR WAS LIFTED INTO THE TREES.

THE TORNADO PATH WAS 2 1/2 MILES LONG...WHILE THE WIDTH WAS ABOUT
200 YARDS. BASED ON THE DAMAGE...THE TORNADO WAS MAINLY AN F2...BUT
RATED AS A WEAK F3 AT ITS PEAK..WITH WINDS OF 160 MPH.

THE FUJITA SCALE RATES TORNADOES ON WIND SPEED AND DAMAGE. THE SCALE
FOLLOWS:

PUBLIC INFORMATION STATEMENT...CORRECTED FOR DATE
NATIONAL WEATHER SERVICE STATE COLLEGE PA
520 PM EDT TUE JUL 22 2003

...STRAIGHT LINE WIND DAMAGE FOUND IN DAUPHIN COUNTY FROM JULY 21
STORM...

A TEAM FROM THE NATIONAL WEATHER SERVICE OFFICE IN STATE COLLEGE
SURVEYED DAMAGE AND INTERVIEWED RESIDENTS AND EMERGENCY MANAGEMENT
OFFICIALS IN DAUPHIN COUNTY TODAY. THE TEAM DETERMINED THAT DAMAGE
IN THE HARRISBURG AREA WAS CAUSED BY STRAIGHT LINE WINDS.

THE THUNDERSTORM PRODUCED WIND GUSTS OF 65 TO 70 MPH IN THE GREATER
HARRISBURG AREA...DOWNING 30 LARGE TREES AND AN ADDITIONAL NUMBER OF
SMALLER TREES. ABOUT 40 CARS WERE DAMAGED BY THE FALLING
TREES...ALONG WITH SOME DAMAGE TO HOMES. THE DAMAGING WIND OCCURRED
BETWEEN 1000 AND 1015 PM.

PUBLIC INFORMATION STATEMENT...CORRECTED FOR DATE
NATIONAL WEATHER SERVICE STATE COLLEGE PA
515 PM EDT TUE JUL 22 2003

...F1 TORNADO CONFIRMED IN MCKEAN COUNTY ON MONDAY JULY 21...

A TEAM FROM THE NATIONAL WEATHER SERVICE OFFICE IN STATE COLLEGE
SURVEYED DAMAGE AND INTERVIEWED RESIDENTS AND EMERGENCY MANAGEMENT
OFFICIALS IN MCKEAN COUNTY TODAY. THE TEAM DETERMINED THAT AN F1
TORNADO DID TOUCH DOWN IN MCKEAN COUNTY BETWEEN 315 PM AND 330 PM
MONDAY AFTERNOON.

THE THUNDERSTORM WHICH SPAWNED THE TORNADO FIRST STARTED PRODUCING
DOWNBURST WIND DAMAGE 2 MILES WEST OF KANE. IT CONTINUED TO THE
NORTHEAST FOR 15 MILES...BEFORE THE TORNADO TOUCHED DOWN 1 MILE WEST
OF THE KINZUA VIADUCT IN A WOODED AREA. THE TORNADO CONTINUED
NORTHEAST...PRODUCING A DAMAGE PATH 3 1/2 MILES LONG...AND ABOUT 1/3
MILE WIDE. WINDS WERE ESTIMATED AT 100 MPH...WHICH CLASSIFIES THE
TORNADO AS AN F1 ON THE FUJITA SCALE. THE TORNADO CAUSED THE
COLLAPSE OF THE HISTORIC KINZUA VIADUCT BRIDGE. NINE OF THE 20
BRIDGE SUPPORTS WERE DESTROYED...LEADING TO THE COLLAPSE OF THE
BRIDGE. THOUSANDS OF TREES WERE ALSO DOWNED ALONG THE PATH OF THE
TORNADO.

THE TORNADO THEN LIFTED UP ABOUT 2 1/2 MILES NORTHEAST OF THE
BRIDGE. DOWNBURST WIND DAMAGE CONTINUED TO ABOUT 2 MILES NORTH OF
SMETHPORT...WHERE THE TORNADO ONCE AGAIN TOUCHED DOWN. THE TORNADO
CONTINUED ON A NORTH-NORTHEAST PATH UNTIL IT LIFTED AGAIN ABOUT 1
MILE NORTH OF FARMERS VALLEY...NEAR THE INTERSECTIONS OF ROUTES 46
AND 446. TOP WIND SPEEDS DURING THE SECOND TOUCHDOWN WERE ESTIMATED
AT 80 TO 90 MPH...AGAIN CLASSIFYING THE STORM AS AN F1 IN INTENSITY.
THE PATH OF THE SECOND TOUCHDOWN WAS ABOUT 3 MILES LONG...WITH A
WIDTH OF ABOUT 150 YARDS.

THIS SECOND TOUCHDOWN DAMAGED 2 BARNS...AND DESTROYED A THIRD. TWO
HOMES AND A CHURCH WERE ALSO DAMAGED. NO INJURIES OR DEATHS WERE
REPORTED.

THE FUJITA SCALE RATES TORNADOES ON WIND SPEED AND DAMAGE. THE SCALE
FOLLOWS:

0500 PM MUNCY
PA WIND DAMAGE
07/21/03 LYCOMING
IN THE AREA FROM A LINE
BETWEEN MUNCY AND
HUGHESVILLE, GOING EAST
TOWARDS LAIRDSVILLE, MANY
TREES REPORTED DOWN.
FRANKLIN TOWNSHIPS REPORTED
DAMAGE TO SHED ROOF AND
TOPS OFF TREES. PENN
TOWNSHIP REPORTED MOST OF
LARGE BARN BLOWN DOWN,
DAMAGE TO CAR AND VAN.

1000 PM KANE
PA FLOOD
07/21/03 MCKEAN
MINOR FLOODING ALREADY
OCCURRING. SOME SMALL
STREAMS ALREADY WERE OUT OF
THEIR BANKS. FLOODING
REPORTED WAS COUNTY WIDE.

1014 PM NEW COLUMBIA
PA WIND DAMAGE
07/21/03 UNION
STRONG WINDS REPORTED.
ROOF TORNED OFF BARN.
SEVERAL TREES DOWN. FIVE
ROADS CLOSED DUE TO TREES
OVER POWER LINES IN THE
EASTERN SECTION OF THE
COUNTY.

0500 PM MUNCY
PA WIND DAMAGE
07/21/03 LYCOMING
IN THE AREA FROM A LINE
BETWEEN MUNCY AND
HUGHESVILLE, GOING EAST
TOWARDS LAIRDSVILLE, MANY
TREES REPORTED DOWN.
FRANKLIN TOWNSHIP REPORTED
DAMAGE TO SHED ROOF AND
TOPS OFF TREES. PENN
TOWNSHIP REPORTED MOST OF
LARGE BARN BLOWN DOWN,
DAMAGE TO CAR AND VAN.

0532 PM MILLERSTOWN
PA WIND DAMAGE
07/21/03 PERRY
NUMEROUS TREES AND WIRES
DOWN WITH MOST CONCENTRATED
AREA OF DAMAGE IN
MILLERSTOWN.

1000 PM KANE
PA FLOOD
07/21/03 MCKEAN
MINOR FLOODING ALREADY
OCCURRING. SOME SMALL
STREAMS ALREADY WERE OUT OF
THEIR BANKS. FLOODING
REPORTED WAS COUNTY WIDE.

1014 PM NEW COLUMBIA
PA WIND DAMAGE
07/21/03 UNION
STRONG WINDS REPORTED.
ROOF TORNED OFF BARN.
SEVERAL TREES DOWN. FIVE
ROADS CLOSED DUE TO TREES
OVER POWER LINES IN THE
EASTERN SECTION OF THE
COUNTY.

THE NATIONAL WEATHER SERVICE INDICATED AN F1 TORNADO STRUCK THE
VILLAGE OF NASSAU IN THE VICINITY OF MCCLELLAN ROAD AND U.S. ROUTE
20.

A DISCONTINUOUS PATH OF THREE QUARTERS OF MILE ENDED JUST NORTH OF
ROUTE 20 WITH MULTIPLE VORTICES INDICATED. THE AVERAGE WIDTH OF THE
TORNADO WAS 75 TO 100 YARDS. THE THUNDERSTORM THAT PRODUCED THIS
TORNADO WAS THE SAME STORM THAT SPAWNED THE F2 TORNADO IN CATSKILL,
GREENE COUNTY.

AN F1 TORNADO PRODUCES WINDS OF 73 TO 112 MPH. AN F2 TORNADO
GENERATES WINDS OF 113 TO 157 MPH.

THERE WAS ALSO STRAIGHT LINE WIND DAMAGE ASSOCIATED WITH THE
THUNDERSTORM IN NASSAU. ALSO...STRAIGHT LINE WIND DAMAGE WAS FOUND
IN THE VICINITY OF KINDERHOOK LAKE...AND ALONG BOTH ROUTE 203 AND
CAMP HOLLY ROAD IN NIVERVILLE. THESE WINDS WERE ESTIMATED IN EXCESS
OF 80 MPH. ADDITIONAL DAMAGE WAS OBSERVED BETWEEN THE VILLAGES OF
KINDERHOOK AND VALATIE ALONG STATE FARM ROAD AND COUNTY ROUTE 21.

THE NATIONAL WEATHER SERVICE INDICATED AN F1 TORNADO STRUCK THE
VILLAGE OF PALENVILLE IN GREENE COUNTY EARLY MONDAY EVENING. THE
TORNADO
AT THIS POINT WAS 50 YARDS WIDE AND WAS ON THE GROUND FOR A HALF A
MILE.

THE TORNADO TOUCHED DOWN AGAIN AND STRUCK THE TOWN OF CATSKILL IN
GREENE COUNTY. AT THIS POINT IT WAS CLASSIFIED AS AN F2 TORNADO WITH
A
PATH WIDTH OF 150 YARDS.

DAMAGE IN NORTHERN ULSTER COUNTY WAS DETERMINED TO BE CAUSED BY
STRAIGHT LINE WINDS.

REPORTS ARE NOT YET AVAILABLE FOR COLUMBIA...RENSSELAER AND
BENNINGTON COUNTIES